Amazon has a huge business in the UK with offices, staff, stock and warehouses, but Amazon UK doesn't sell stuff. You are actually buying UK goods from UK warehouses with UK delivery etc but the money goes straight to Amazon EU Sarl in Luxembourg, where it has a sweetheart tax deal.
So Amazon exploits the whole UK social system of education, health services, roads, police etc etc without paying the UK government for the benefits. This is really bad for the UK and other countries except Luxembourg.
Meanwhile, Amazon EU Sarl reduces its taxes by paying Amazon Europe Holding Technologies SCS - a "non-resident" company -- hundreds of millions of euros for "intellectual property" rights that are basically untaxed (Amazon is paying itself), and the money gets spirited back to the USA.
The cost of "intellectual property" is really just a made-up number. What is Amazon charging itself vast amounts of money for when its UK website and business processes are basically the same as its American and other websites?
The whole thing may be legal but it's basically a fraud, and the EU ordered EU ordered Amazon to repay €250m in “illegal tax advantages”. Which is still chickenfeed for a company of Amazon's size and wealth.
It's highly likely that European countries will introduce a "digital tax" on turnover to stop this kind of cheating. I expect Americans will get angry if or when that happens, but in the long run, we don't have an alternative. Infrastructure is expensive, and the money should come from the people who are benefiting from it.
In the US, of course, Amazon gets tax breaks from people who want Amazon investment. New Jersey offered $7bn of tax incentives in its bid for Amazon's "second headquarters".
If companies like Amazon actually paid the taxes required by law that would be nice. Instead they have armies of people finding wholly artificial ways to legally avoid paying those taxes.